Antioxidant, Cytotoxicity, and Antiophidian Potential of Alstonia macrophylla Bark

[Image: see text] The objective of this research was to find the possible pharmacognosy of the bark of the Philippine Alstonia macrophylla Wall. ex G.Don (AM). Gas chromatographic–mass spectral (GC–EI-MS) characterization and energy dispersive X-ray spectroscopy (EDX) were performed to detect the bioactive constituents. EDX analysis of AM bark displayed a high content of potassium (3.26%) and calcium (2.96%). Eight constituents were detected in AM crude dichloromethane (DCM) extracts, which consisted of a long-chain unsaturated fatty acid (17:0) and fatty acid esters such as ethyl hexadecanoate and methyl hexadecanoate. Extraction of AM bark using methanol and dimethyl sulfoxide (MeOH/DMSO) solvents resulted in the identification of 17 constituents, principally alkaloids (alstonerine, 34.38%; strictamin, 5.23%; rauvomitin, 4.29%; and brucine, 3.66%) and triterpenoids (γ-sitosterol, 3.85%; lupeol, 3.00%; 24-methylenecycloartanol, 2.81%; campesterol, 2.71%; β-amyrin, 2.30%; and stigmasterol, 2.13%). MeOH/DMSO samples of AM were used in the selected bioassays. The samples exhibited efficient free radical scavenging activity (IC(50) = 0.71 mg/mL) and were noncytotoxic to normal HDFn (IC(50) > 100 μg/mL) and neoplastic THP-1 cell lines (IC(50) = 67.22 μg/mL) while highly degenerative to MCF-7 (IC(50) = 6.34 μg/mL), H69PR (IC(50) = 7.05 μg/mL), and HT-29 (IC(50) = 9.10 μg/mL). Most interestingly, the AM samples inhibited the northern Philippine Cobra’s (Naja philippinensis Taylor) venom (IC(50) = 297.27 ± 9.33 μg/mL) through a secretory phospholipase A(2) assay.